The research, conducted by Goldman with Hiram Beltrán-Sánchez and Anne Pebley at the University of California, Los Angeles, finds this to be especially true in middle-income countries like Mexico, where occupational health and safety regulations are weak or were enacted comparatively recently.

Poor people are considerably more likely to suffer from limited mobility as they age. Previous research has demonstrated a relationship between disability among older adults and factors that poor people experience disproportionately, such as childhood adversity, lack of access to health care, harmful behaviors, unhealthy and unsafe neighborhoods and stress both on and off the job, Goldman said.

But disadvantaged people also are more likely to hold jobs that require heavy physical labor, repetitive movement, strain on the body and safety hazards. "This is particularly true in low- and middle-income countries where workers with little education and low income often face multiple health conditions that lead to higher disability over their lifetimes," Beltrán-Sánchez said. The researchers sought to determine whether people's primary occupations contribute to the unequal distribution of disability among older adults.

They focused on Mexico, Goldman said, because it's a middle-income country with a diverse economy that, like many other countries, has a rapidly growing older population. "With growing segments of the population experiencing functional limitations and disability, the country is facing a serious health policy challenge," said Goldman. Moreover, in countries like Mexico that have weaker occupational safety and health regulations, physical job demands are typically harsher and a higher proportion of people work in the unregulated informal sector of the economy.

Beltrán-Sánchez, Pebley and Goldman analyzed responses from the Mexican Health and Aging Study, which began surveying about 15,000 older Mexican citizens in 2001. After filtering out survey respondents who didn't meet their criteria, they developed a nationally representative sample of more than 12,000 people aged 50 or older in all 32 Mexican states, about 54 percent of whom are women and 46 percent men.

Survey respondents were asked to name the main job that they'd held during their lives. The researchers organized the jobs into categories with similar physical demands, then looked for associations between those categories and mobility limitations among people over age 50.

Two job categories, they found, were most strongly associated with limited mobility: domestic workers and food/beverage/tobacco workers, both of which had an average of more than three mobility limitations. Workers in a larger group of categories -- including agricultural laborers and repair and maintenance workers, among others -- averaged two to three physical limitations. Workers in less physically demanding jobs that are typically held by people higher on the socioeconomic spectrum, such as managerial positions, had fewer limitations on average.

But because poor people are generally less healthy than wealthier people, the question is whether certain job categories are associated with disability among older adults simply because they are held by poor people, or whether the jobs themselves are contributing to the disability. In other words, if wealthier people worked in similarly physically demanding jobs, would they also have more functional limitations as they age? To find out, Beltrán-Sánchez, Pebley and Goldman controlled for socioeconomic status (measured by education and wealth) in their analyses. They found that in fact, with controls for socioeconomic status, job categories were still associated with mobility limitations as people grew older.

Nevertheless, physically demanding jobs are overwhelmingly held by poorer people, compounding the problem of health disparities. Thus, Pebley said, "For policy makers in Mexico and elsewhere concerned about social inequality in health, our results suggest that a greater focus on improving conditions in the workplace could be a cost-effective investment for reducing mobility limitations among older adults."

The study appears as Hiram Beltrán-Sánchez, Anne Pebley and Noreen Goldman, "Links Between Primary Occupation and Functional Limitations Among Older Adults in Mexico" in SSM -- Population Health, Vol. 3 (December 2017), pp. 382-392. It was published online in April 2017.

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The work was supported by grants from the National Institute on Aging (R01AG052030), a pilot grant from the USC-UCLA Center on Biodemography and Population Health (P30AG017265), and grants from the Eunice Kennedy Shriver National Institute of Child Health and Human Development to the California Center for Population Research at UCLA (P2CHD041022) and to the Office of Population Research at Princeton University (P2CHD047879).

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